Effects of a 16-week recreational small-sided games soccer intervention on body composition and physical fitness in sedentary young adults: A randomized controlled study

Recreational small-sided games (SSGs) have demonstrated positive effects on body composition and physical fitness, while minimizing adverse outcomes. In this randomized controlled study, we aimed to investigate the impact of incorporating an additional 16-week intervention program involving recreational soccer SSGs on parameters related to body composition and physical fitness in sedentary young adult males and females. Sixty sedentary participants, with a mean age of 20.2 years, were randomly assigned to either the small-sided games group (SSG; n = 30) or the active control group, which participated in regular physical education classes (CG; n = 30). The SSG group engaged in the same activities as the control group but additionally participated in a recreational SSG football program. This program involved continuous and intermittent moderate-to high-intensity exercises conducted on 20 m × 30 m and 30 m × 50 m football fields. In contrast, the CG group received 1 h of physical education once a week. The interventions were administered for a duration of sixteen weeks. Baseline, 8-week, and post-intervention assessments were conducted to measure body mass (BM), body mass index (BMI), waist circumference (WC), hip circumference (HC), waist-to-hip ratio (WHR), skinfold thickness (SFT), standing broad jump (SBJ), vertical jump (VJ), handgrip strength (HG) for both left and right hands, shuttle run distance (SRD), and shuttle run estimated VO2max. Results indicated that both male and female participants in the SSG group exhibited significant improvements in BM, BMI, SFT, WC, HC, and WHR following the intervention (p < 0.05), whereas the control group demonstrated no significant changes over the study period (p > 0.05). Additionally, SSG participants (regardless of sex) displayed significant enhancements in SBJ, VJ, HG, SRD, and VO2max (p < 0.05), while the control group did not exhibit any significant alterations (p > 0.05). The findings from this experimental study suggested that a 16-week recreational soccer SSG intervention effectively enhanced body composition and physical fitness among overweight sedentary young adults, offering a pleasurable alternative to conventional training approaches.


Introduction
The prevalence of sedentary behavior among young adults has become a growing concern on a global scale, as evidenced by numerous scientific reports and findings [1].Sedentary lifestyles, characterized by prolonged periods of sitting or low levels of physical activity, have become increasingly prevalent in this demographic [2].Research consistently highlights the detrimental consequences of sedentarism, demonstrating a strong association with an elevated risk of non-communicable diseases [3].Studies indicate that sedentary behavior is linked to an increased likelihood of developing conditions such as cardiovascular diseases [4], diabetes, and obesity [5].Furthermore, a sedentary lifestyle is intricately connected to a decrease in fitness levels and overall health [6].The lack of physical activity contributes to reduced cardiovascular fitness, muscle strength, and flexibility, adversely affecting the physiological well-being of young adults [3].Addressing the sedentary epidemic through evidence-based interventions is crucial to mitigate the risk of non-communicable diseases and promote overall health in this population [7].
Scientific evidence consistently underscores the efficacy of physical exercise, particularly intense intermittent exercise, in enhancing physical fitness and positively influencing body composition [8].High-intensity intermittent exercise, such as interval training, has been shown to significantly improve cardiovascular fitness [9], increase muscle strength, and enhance metabolic function [10].These adaptations not only counteract the detrimental effects of sedentary behavior but also contribute to favorable changes in body composition by reducing body fat and increasing lean muscle mass [11].
Scientific evidence highlights the transformative potential of recreational soccer (as a form of intermittent intense exercise) in community programs as a compelling strategy to counter sedentary behavior while promoting health and fitness [12] (ref).Participating in recreational soccer not only engages sedentary populations in enjoyable physical activity but also fosters a social environment, addressing key factors that contribute to sustained participation [13].Research indicates that recreational soccer, with its dynamic nature and intermittent bursts of high-intensity effort, mirrors the benefits of structured high-intensity interval training [14].This form of exercise has been associated with improved cardiovascular fitness [12], enhanced metabolic health [15], and favorable body composition changes [16].Moreover, the communal and enjoyable aspects of soccer contribute to increased adherence to physical activity, positively impacting mental well-being and overall quality of life [17].By incorporating recreational soccer into community programs, evidence-based approaches align with both the physiological and social dimensions, offering a holistic solution to combat sedentary lifestyles and promote lasting health benefits [18].
Current scientific findings underscore the efficacy of recreational soccer in positively influencing body composition and physical fitness across diverse age groups, particularly in young [19] and older populations [20].However, there exists a notable gap in our understanding of the impact of recreational soccer on body composition and physical fitness in the critical transitional phase of young adulthood, characterized by the shift from high school to university.This demographic is particularly susceptible to declines in physical activity, potentially exacerbating sedentary behavior [21].While the benefits of recreational soccer are well-established in other age brackets, further research is warranted to comprehensively elucidate its effects on body composition and physical fitness in young adults during this crucial life transition.Closing this knowledge gap could inform targeted interventions to mitigate sedentary trends and optimize health outcomes in this specific population.
To address this gap in the literature, the present study aimed to investigate the potential benefits of a 16-week recreational soccer small-sided games (SSGs) program on body composition-related parameters and physical fitness in sedentary young adult males and females.A control group, only enrolled in one physical education class a week, was also included for comparison purposes.Building on prior research [22,23], our hypothesis posited that individuals exposed to recreational soccer SSGs experienced a significant improvement in body mass index, fat mass, endurance performance, and neuromuscular performance compared to the control group.

Experimental design
This investigation utilized a randomized controlled two-arm study design and lasted for 16 weeks.Evaluations were conducted at baseline, the midpoint (8th week), and the end of the 16 weeks.This study employed a per protocol analysis, which considered attendance at all evaluations and sessions, as well as non-enrollment in specific diets.Initially, 10 universities were contacted based on geographic location, and seven of them agreed to participate in the study.All students who met the inclusion criteria were invited to participate, resulting in a participation rate above 85 %.The final participants were registered in the system, the experiment was carried out in January 2023 and data collection for all participants was completed in the end of April 2023.The researchers ensured the accuracy of the experiment by using the same test methods and tools across all participating schools.The participants were randomly assigned to either the SSGs group or the control group using a simple randomization process involving the use of letters.Allocation concealment was rigorously ensured through centralized randomization and sealed envelopes, bolstering the reliability and impartiality of treatment assignments in the experiment.The procedure was carried out by an assessor who was blinded to the experiment.
Participants were mandated to attend training sessions held at the specified experimental site, facilitated by the research team.Moreover, participants were directed to adhere to a dietary regimen tailored for obese individuals throughout the study.It is noteworthy that neither participants, assessors, nor instructors were blinded to the experiment.
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Participants
Recruitment involved reaching out through social media and networks, where individuals expressing interest voluntarily participated in the experiment.To accommodate potential dropouts and enhance sensitivity to smaller differences, a total of 84 subjects were recruited.Of these, 8 participants did not meet the eligibility criteria, and 16 participants failed to complete the training.Ultimately, 60 participants completed the entire experiment, with 30 in the SSGs group and 30 in the control group.
The study comprised university students residing in diverse urban areas of Nanchang, China, an eastern city in the country.Inclusion criteria mandated that participants be sedentary men or women with overweight or obesity (BMI >28) and devoid of other health issues.Attendance at all three assessments (anthropometry, cardiovascular, and musculoskeletal fitness), maintenance of a training program adherence exceeding 75 %, and non-enrollment in additional nutritional or pharmacological strategies for weight loss were also prerequisites.Detailed participant characteristics are provided in Table 1, while the participant enrollment and retention process is delineated in Fig. 1.
Prior to participation, every participant received comprehensive information about any potential risks or discomfort associated with the experiment.Upon agreement to participate, the guardians provided their consent by signing a consent form.The study adhered to ethical standards for medical research involving human subjects as outlined in the Declaration of Helsinki.Ethical approval for the study was obtained from the Institutional Ethical Review Board of Chengdu Institute of Physical Education, with reference code 2023#104.

Methodological procedures
In the initial session, demographic data were collected, and participants' physical activity levels were assessed using the short form of the International Physical Activity Questionnaire [24] as a secondary outcome.Sedentary levels were determined based on participants' scores.
Furthermore, throughout the study (during the 3rd, 6th, and 9th weeks), participants were closely monitored to assess their physical activity (PA) levels.This monitoring aimed to ensure that they were not engaging in activities beyond the scope of the expected ones.Upon conducting exploratory analysis, no discernible differences were observed in the behaviors of participants, both within the experimental and control groups, even after adjusting for the implemented training programs.
In the second evaluation phase, a battery of tests assessing anthropometric measurements, body composition, and physical fitness was administered by a team of assessors.The team comprised four sports scientists, each holding at least a master's degree and possessing extensive experience in physical fitness and anthropometry assessments.
The initial anthropometric and physical fitness test occurred at 3:00 p.m. on December 8, 2022, in the gymnasium of the author's workplace, with a temperature of 5 • C and relative humidity at 53 %.Anthropometric measurements were initiated, with participants measured in the order of their registration.Subsequently, the physical fitness tests began 10 min after anthropometry, following this sequence: (i) handgrip strength test; (ii) standing broad jump; (iii) vertical jump tests; and (iv) the 20-m shuttle run test.Three minutes of rest interspersed between each of the physical fitness tests.Baseline testing occurred at the 8th and 16th weeks at the same location as the initial test.

Anthropometry and body composition
Anthropometric measurements were conducted on participants following standardized procedures.Stature was measured using the Seca digital weighing scales stadiometer (803, Seca, China) with a technical error of ±0.1 kg.Measurements were taken with participants barefoot and wearing regular shirts and shorts.Body mass was measured using the Smart Body Analyzer (WS-50, Withings, France) with a technical error of ±0.5 cm.The body mass index (BMI) was subsequently calculated using the measured values of stature and body mass.
A highly trained and standardized technician, following recommended protocols, measured skinfold thickness [25].Subscapular, suprailiac, triceps, biceps, and thigh skinfold measurements were assessed.The caliper (Lange Skinfold Caliper, Beta Technology Incorporated, Cambridge, MD) was applied 1 cm below the thumb and finger holding the fold, and thickness was recorded to the nearest 0.1 cm.All skinfold measurements were taken three times, and the average was recorded [26].
Waist circumference was measured by identifying the top of the hip bone and the bottom of the ribcage, measuring at the level midway between these landmarks.Hip circumference was measured at the widest part of the hips, typically at the level of the greater trochanters.In summary, the primary outcomes considered for the current study encompassed body mass, BMI, waist circumference, hip circumference, waist-to-hip ratio, and skinfold thickness.
Under professional guidance, stature, body mass, waist circumference, and hip circumference were measured once, and skinfold thickness was measured three times.A single researcher, with expertise in anthropometric assessment and a demonstrated high level of reliability (±0.5 cm), performed all measurements.The MPS Micro rope displacement sensor (XXS, MILONT, China) with a technical error of ±0.1 cm was used by the researcher to ensure precision in the measurement process.

20-m shuttle run test
The 20-m shuttle run test was administered to participants following the original protocol previously published [27].Participants were directed to run back and forth between two lines placed 20 m apart, pivoting around a central point situated between the two lines.Instead of crossing the line before turning, participants had the option to spin and continue running within the boundaries of the two lines.The test concluded if the participant failed to reach a line after two consecutive beeps or if the participant neglected to wait for the beep twice in a row.The total distance covered by each participant was recorded as the primary outcome.Additionally, VO2 max was estimated using the equation VO2max = − 24.4 + 6.0 final velocity achieved.It is noteworthy that the 20-m shuttle run, also recognized as the Buzzer test, has been validated as a reliable tool for predicting the maximal oxygen uptake (VO2max) and is widely acknowledged as the gold standard for field-based assessments of aerobic fitness [28].The primary outcomes for the current research included the shuttle run distance and estimated VO2max.

Handgrip dynamometry
After comparing the Jamar, DynEx, and TKK precise dynamometers, handgrip strength was evaluated using the TKK dynamometer (TKK 5101 Grip-D, Takey, Tokyo, Japan), identified as the most accurate among the three.In terms of criterion-related validity, the Jamar and DynEx dynamometers were found to underestimate handgrip strength levels by − 192 and 21.43 kg, respectively.The TKK dynamometer exhibited the lowest level of systematic error (0.49 kg) and is thus deemed the most appropriate tool for assessing handgrip strength within the studied population [29].
Participants were instructed to extend their arms, using their dominant hand to exert maximal force on the dynamometer.The grip had to be sustained for at least 2 s, and the task was repeated twice, with the peak force recorded for analysis.Each participant underwent 3 trials per hand, with a 2-min rest between trials and a 3-min rest between hands.The trial producing the highest value was utilized for statistical analysis.The average coefficient of variation for the within-participant (variability between trials) analysis was 2.1 % in the handgrip strength.The primary outcomes for the current research involved the maximal handgrip strength in both left and right hands.

Standing broad jump and vertical jump
The My Jump 2 app on iPhone X was employed to calculate jump height by manually selecting the take-off and landing frames of the video.The app utilizes the equation: as described by Bosco et al. [30], where h represents jump height (in meters) and t denotes flight time (in seconds).My Jump 2 was employed to measure jumping performance, as it has been demonstrated to be a valid and reliable tool for assessing both jump height and jump length [31].
For the vertical jump, participants were instructed to initiate the jump [32] from a position of 90 • knee flexion [33], with feet shoulder-width apart and hands on their hips.They were directed to jump for maximum height while keeping their hands on their hips [34].In the standing broad jump, participants were positioned on the start line and instructed to jump horizontally as far as possible while maintaining hands on hips.Swinging arms during the jump was not permitted.Successful jumps required participants to land on both feet without secondary corrective motions [35].Each participant performed both jumps three times, with a 2-min rest between trials and a 3-min rest between jump tests.The trial producing the highest value was used for statistical analysis.The average coefficient of variation for the within-participant (variability between trials) analysis was 3.4 % in the vertical jump and 3.7 % in the standing broad jump.
The primary outcomes for the current research included the highest vertical and horizontal jumps.

Training intervention
The SSGs intervention consisted of five weekly sessions held over the period of experiment, each lasting 60 min.This additional training was incorporated alongside the participants' regular 1-h weekly physical education.The control group, in contrast, did not

Table 2
The characteristics of small-sided games intervention.undergo any specific training and continued with their regular daily activities, including a standard diet and 1 h of weekly physical education.
SSGs training sessions occurred on the school football field after regular class hours.A 10-min warm-up preceded 40 min of smallsided games and technical drills, concluding with 10 min of cool-down exercises.To ensure consistent training intensity and participant safety, each individual wore a heart rate monitor (Polar RS400, Kempele, Finland) during every session.Participant maximal heart rate (HRmax) was calculated using the Ruffier test [36], and two college physical education teachers, under the author's guidance, assisted in conducting the experiment.
Exercise perceived intensity was assessed using the Borg CR 10 Scale and the Talk Test [37].Additionally, participants completed a personal exercise monitoring card after each session to track health status and exercise levels.The card included the date, type, and duration of the recreational soccer training, subjective assessment of exercise intensity (Borg CR 10 Scale), physical health before and after training, rest time post-training, and reasons for any missed sessions.
The SSGs intervention targeted major muscle groups and cardiopulmonary function with exercises such as shuttle runs, sprints, passing, jumps, dribbling, and shooting.For the initial eight weeks, the exercise-to-rest ratio was set at 5:1 based on individual athletic ability and training progress.At the midpoint of the 16-week intervention, we assessed participants' exercise levels and physical health, adjusting the exercise-to-rest ratio and training type for the subsequent eight weeks accordingly.Table 2 provides a detailed breakdown of workout and rest intervals, along with the type of training, during the intervention.The participants in the SSG group were assigned to teams based on their proficiency levels, with adjustments made as necessary to ensure the games remained as competitive as possible.The selection process was overseen by the trainer in charge, who has experience in community programs and soccer.The games were organized by sex, with men competing against men and women facing off against women.
The SSGs intervention comprised a total of 80 sessions conducted at the school's football stadium, where the author is employed.These sessions occurred on Mondays, Wednesdays, and Thursdays from 4:30 p.m. to 5:40 p.m., and on Fridays and Saturdays from 6:30 p.m. to 7:40 p.m. Throughout each session, the participants' physical condition and movement status were diligently monitored.The author supervised the implementation of the training program, with two additional teachers offering technical corrections and encouragement to the participants.
The percentage of adherence in the SSG interventions was 90.0 ± 1.0 % in men (91 % between the first and second assessment and 89 % between the second and third assessment), while it was 89.5 ± 2.5 % in women (92 % between the first and second assessment and 87 % between the second and third assessment).

Statistical procedures
The study's sample size was determined utilizing G*Power 3.1 software (Düsseldorf, Germany), specifically selecting the ANOVA: Repeated measures, Within-between interaction option.Power, α, and effect size were set at 0.8, 0.25, and derived from previous studies [38,39].Results revealed that the overall effect size of Matrix Factorization on the competitive ability of football players predominantly falls within the range of 0.50-2.37,with an average effect size of 0.84.A minimum of 22 participants per group was deemed necessary for this study.
Descriptive statistics are presented as mean and standard deviation.Normality and homogeneity were assessed using the Kolmogorov-Smirnov and Levene's tests, respectively.The Smallest Worthwhile Change (SWC) was determined using Cohen's effect size principle, a measure that indicates the magnitude of change deemed meaningful.The formula utilized was: , where SD 2 1 and SD 2 3 represent the standard deviations of the measurements for the "1st" and "3rd" tests, respectively.This calculation was performed for each variable, considering a sample size of 30 participants.The resulting SWC values represent the smallest change in each variable that is considered meaningful within the context of the study.
Once normality and homogeneity were confirmed (p > 0.05), an independent t-test and Cohen's d effect size test were performed to compare the baseline levels between groups.A mixed ANOVA (times * group) was used to examine interactions between factors, with partial eta squared used to estimate effect sizes.Pairwise comparisons were analyzed using Bonferroni's post hoc test.Cohen's d was also calculated to determine the magnitude of differences in pairwise comparisons.All statistical analyses were performed using SPSS software (version 28.0.0.0,IBM, Chicago, USA) with a significance level set at p < 0.05.

Baseline assessments
In men, there were no significant differences between groups in the baseline levels of body mass (p = 0.  A: assessment; SWC: smallest worthwhile change; #: significantly different from 1stA at p < 0.05; ¶: significantly different from 2ndA at p < 0.05; @; significantly different from 3rdA at p < 0.05.

Anthropometry and body composition
Table 3 presents the descriptive statistics of participant anthropometry and characteristics across the three assessment time points in the experimental study.Supplementary Material 1 illustrates the variation among participants (within-participation variation) across assessments, taking into account anthropometric and body composition variables.No significant interactions on body mass (F =

Table 4
Descriptive statistics, presented as mean ± standard deviation, used to report participant characteristics across the three assessment time points in the experimental study.[48], promoting improvements in aerobic fitness over time.The dynamic nature of SSGs necessitates rapid shifts between aerobic and anaerobic energy systems, engaging both oxidative and glycolytic pathways [42].This metabolic versatility places a demand on the cardiovascular system to deliver oxygen to working muscles efficiently, thereby enhancing the cardiovascular response.Moreover, the variability in movement patterns and intensities during SSGs stimulates the recruitment of diverse muscle groups, fostering a comprehensive physiological adaptation [49].This multifaceted approach, targeting both cardiovascular and muscular systems, contributes synergistically to the improvements in aerobic performance observed with regular participation in small-sided games.Engaging in SSGs, particularly those with fewer players and confined spaces, triggers specific neuromuscular adaptations that are associated with heightened lower-limb power as demonstrated previously in recreational soccer [20].The dynamic nature of SSGs involves swift and repetitive accelerations and decelerations, presenting challenges to the neuromuscular system [50].These challenges prompt adjustments in muscle recruitment patterns, potentially leading to enhanced efficiency in fiber recruitment.
The specific movement patterns intrinsic to SSGs, characterized by rapid changes in direction and velocity, closely replicate the mechanics of jumping.This replication involves capitalizing on overcoming inertia through force application and, in the case of vertical jumps, exploiting the stretching-shortening cycle [50].The overload imposed by the acceleration and deceleration demands in SSGs may stimulate physiological responses crucial for enhancing lower-limb power.This includes heightened motor unit recruitment and improved capabilities in force production.

Study limitations, future research and practical applications
The present study has certain limitations.One factor is the absence of alternative experimental training programs (e.g., involving other recreational sports or utilizing analytical approaches) to assess the effectiveness of the current program compared to a similar physical exercise regimen.Another limitation stems from the initially low baseline levels; hence, the incorporation of a high-volume program, as implemented, may have contributed to the observed improvements.Future research should explore comparisons among multiple intervention programs and test various training volumes with the goal of determining the optimal dosage relative to baseline conditions.Additionally, monitoring training load and examining associated changes post-intervention can contribute to a more comprehensive understanding of the mechanisms underlying these improvements.
In terms of practical applications, the current study demonstrates that community-based training programs centered around smallsided games can enhance the physical fitness and body composition of sedentary young adults.Governments and universities may consider establishing facilities and community programs to engage young adults within their own contexts, fostering a community that remains motivated to enhance their health and improve overall well-being and lifestyle.These programs should emphasize offering 2 to 3 training sessions per week, each lasting at least 45 min.During these sessions, participants should be involved in small-sided games that elicit, on average, efforts exceeding 80 % of their maximal heart rate or a perceived exertion rating of 7.5-8 on a 10-point scale.The games should involve a smaller number of players (3v3 to 5v5), utilize small goals (to increase the importance of being close to the finalization zone), and adopt intermittent formats to allow participants to recover actively during periods of exertion.

Conclusions
This study unveiled that participants engaging in SSGs experienced significant reductions in body mass, BMI, waist circumference, hip circumference, waist-to-hip ratio, and skinfold thickness after the intervention.In contrast, the control group exhibited no significant changes during the observation period.Furthermore, the intervention led to improvements in VO2max as well as running and jumping ability.
These findings suggest that a recreational SSGs intervention has a more pronounced impact on physical fitness parameters among sedentary overweight young adults.Additionally, the intervention holds promise for promoting exercise programs in populations with limited access to sports facilities.Importantly, the study underscores the notion that SSGs can serve as an enjoyable and effective exercise strategy for enhancing physical fitness and improving body composition.Ultimately, this intervention could play a crucial role in safeguarding sedentary overweight populations from the heightened risk of non-communicable diseases associated with obesity and inactivity.

Data availability
The data is accessible upon request from the corresponding author.Additionally, to ensure replicability, details of the specific exercise dynamics are also obtainable upon request from the corresponding author.

Fig. 1 .
Fig. 1.Flowchart of participant selection.SSGs: small-sided games, football-themed recreational small side games.Control: normal diet and participation in normal physical education control group.
on a 30 m × 20 m field, set up a 0.5 m high net in the middle of the pitch (football tennis) on a 50 m × 30 m field Min: minutes.Q. Xu et al.

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Table 1
Characteristics of the study participants.

Table 3
Descriptive statistics, presented as mean ± standard deviation, used to report participant characteristics across the three assessment time points in the experimental study.